Why do people disagree

Imagine a debate in philosophy between two people Lets say Dennett and Chalmers.
What is standing in the way of their agreeing?
well to go through the psychological list
1) they are 'supposed to' disagree
but that isn't very useful so we will skip over that
2) because they want different things
maybe for some reason Chalmers is more comfortable with qualia existing and Dennett is not - one strategy if debate would be to expose that and call it a bias
3) because they have a different set of assumptions
any belief that you might have is built on a series of assumptions - in thecase of dennet and chalmers a huge network of assumptions that describe different worlds in sense. But neither side initially knows exactly what those assumptions are. So I might wonder "if I disprove X (where X is a fact that seems to support your conclusion) will your world view come tumbling down or will you just say - I don't really care then y must be true"
So what strategies does each side have open to them? well they will probably run through each of the other person's assumptions and tackle them.
these assumptions will hide in the definitions of words and implicitly ignoring other words

[to be continued and refined]